The present invention relates generally to a turbine engine cooling component such as a shroud cooling segment useful in turbine engines such as high pressure turbines. The present further relates to a turbine cooling subassembly that uses a pair of such turbine components in combination with at least one spline seal.
To increase the efficiency of gas turbine engines, a known approach is to raise the turbine operating temperature. As operating temperatures are increased, the thermal limits of certain engine components can be exceeded, resulting in material failure or, at the very least, reduced service life. In addition, the increased thermal expansion and contraction of these components adversely affects clearances and their interfitting relationships with other components of different thermal coefficients of expansion. Consequently, these components should be cooled to avoid potentially damaging consequences at elevated operating temperatures.
It is common practice then to extract from the main airstream a portion of the compressed air at the output of the compressor for cooling purposes. So as not to unduly compromise the gain in engine operating efficiency achieved through higher operating temperatures, the amount of extracted cooling air should be held to a small percentage of the total main airstream. This requires that the cooling air be utilized with the utmost efficiency in maintaining the temperatures of these components within safe limits.
A particularly important component subjected to extremely high temperatures is the shroud located immediately downstream of the high pressure turbine nozzle from the combustor. The shroud closely surrounds the rotor of the high pressure turbine and thus defines the outer boundary of the extremely high temperature, energized gas stream flowing through the high pressure turbine. To prevent material failure and to maintain proper clearance with the rotor blades of the high pressure turbine, adequate shroud cooling is an important concern.
Shroud cooling is typically achieved by impingement cooling of the back surface of the shroud, as well as by drilling cooling holes that extend from the back surface of the base of the shroud and through to the forward or leading shroud, the bottom or inner surface of the base in contact with the main (hot) gas stream and the side panels or rails of the shroud to provide both convection cooling inside the holes, as well as impingement and film cooling. See, for example, commonly assigned U.S. Pat. No. 5,169,287 (Proctor et al), issued Dec. 8, 1992, which shows an embodiment of shroud cooling of the high pressure turbine section of one type of gas turbine. This cooling minimizes local oxidation and burning of the shrouds near the hot main or core (hot) gas stream in the high pressure turbine. Indeed, the cooling holes that exit through the side panels of the shroud of commonly assigned U.S. Pat. No. 5,169,287 can provide important impingement cooling to the side panel of the adjacent shroud.
While impingement cooling of the entire length of the side panel of the adjacent shroud is desirable, it has been found to be particularly important to provide impingement cooling to the side panels from about the midsection of thereof forward to the leading edge of the shroud, and especially in the region of the midsection of this side panel. It has been discovered that, for some high pressure turbines, the hottest point of the main gas stream tends to localize in the region around this midsection. This means that the greatest opportunity for undesired oxidation and burning of the shroud can occur at this point.
One approach to shroud cooling is disclosed in commonly assigned U.S. Pat. No. 5,169,287. See, in particular, FIG. 2 of U.S. Pat. No. 5,169,287 which shows a pattern of three rows cooling holes or passages 82, 84 and 86 that are formed in shroud segment 22 and extend from back surface 44a of base 44 and exit through the inner surface 44b of base 44, the forward or leading edge or end 45 and one side panel or rail 50. As also shown in FIG. 2 of U.S. Pat. No. 5,169,287, a majority of these cooling passages are skewed in a direction such that the exit holes are opposed to the direction of the main gas stream to minimize the ingestion of the hot gases from this stream into the passages of rows 82, 84 and 86. The set of three passages, indicated by 88, that exit through the one side panel 50 provide a flow of cooling air that impinges against the side panel of the adjacent shroud segment. However, because the cooling passages exit through only one of the side panels, impingement cooling is provided to only one of the side panels of each adjacent pair of shrouds in the shroud assembly of U.S. Pat. No. 5,169,287.
Another prior approach to shroud cooling is shown in FIG. 1 of the present application. The prior shroud of FIG. 1 has a pattern of three rows of cooling holes or passages 182, 184 and 186 that are formed in shroud segment 122 that again exit from the inner surface of base 144, the forward or leading edge or end 145 and one side panel or rail 150. A set of five passages, indicated by 188, exit through one of the side panels 150 but in direction perpendicular to this side panel and also perpendicular to the main gas stream. As a result, there is a tendency for these passages 188 in the prior shroud of FIG. 1 to ingest hot gases from this stream, thus increasing the chance of undesired oxidation and burning of the shroud. Also, and like the shroud disclosed in U.S. Pat. No. 5,169,287, the cooling passages 188 again exit through only one of the side panels of the prior shroud of FIG. 1, so that impingement cooling is provided to only one of the side panels of each adjacent pair of shrouds in the shroud assembly.
As shown in FIG. 2 of the present application, the side panels 150 of the prior shroud of FIG. 1 has three spline seal slots formed therein hereinafter referred to as bottom spline seal slot 192, top spline seal slot 194 and back spline seal slot 196. Each of these slots 192, 194 and 196 receive one edge, respectively, of the bottom, top and back spline seals (not shown) that are positioned in the gap between each adjacent pairs of shrouds. These spline seals generally conform to or assume the same shape as the respective slots 192, 194 and 196 and extend generally the length each of the respective side panels 150 from the forward or leading edge or end 145 to the aft or trailing edge or end 148 of the shroud. As also shown in FIG. 2, bottom slot 192 has a plateau shaped or xe2x80x9chumpedxe2x80x9d section 198 that curves upwardly in the forward section of the shroud before reaching exit holes 188, extends across and above holes 188, and then curves downwardly once past holes 188 in the aft section of the shroud. The bottom spline seal received by slot 192 also generally conforms to the shape of section 198 and thus has a xe2x80x9chumpedxe2x80x9d or xe2x80x9choodedxe2x80x9d section. As a result, the cooling air exiting holes 188 tends to be localized in the region of this humped section 198 of the bottom spline seal.
Yet another prior approach to shroud cooling is shown in FIG. 3 of the present application. The prior shroud of FIG. 3 has a pattern of three rows of cooling holes or passages 282, 284 and 286 that are formed in shroud segment 222 and again exit through the inner surface of base 244, the forward or leading edge or end 245 and one side panel or rail 250. A set of three passages, indicated by 288, extend through one of the side panels 250, the one closest to the leading edge 245 being skewed in a direction opposed to the main gas stream, the next passage being perpendicular to this side section and also perpendicular to the main gas stream and the last passage closest to the aft or trailing edge or end 248 being skewed in a direction that generally follows the main gas stream. Another set of two passages, indicated by 289, extend through the other side panel 250, both passages being perpendicular to this side panel and also perpendicular to the main gas stream. Because passages 288 and 289 exit through both side panels 250, the prior shroud shown in FIG. 3 provides impingement cooling to both of the side panels of each adjacent pair of shrouds in the shroud assembly. However, because one or two of the passages for each of the sets 288 and 289 are perpendicular to the side panels 250 and are located in the midsection of side panels 250 (i.e., the hottest point of the main gas stream), the prior shroud of FIG. 3 will again tend to ingest hot gases from this stream, thus increasing the chance of undesired oxidation and burning of the shroud.
As shown in FIGS. 4 and 5 of the present application, each of the side panels 250 of the prior shroud of FIG. 3 has two spline seal slots hereinafter referred to as bottom spline seal slot 292 and top spline seal 294 that again extend generally the length each of the respective side panels 250 from the forward or leading edge or end 245 to the aft or trailing edge or end 248 of the shroud. Again, each of these slots 292 and 294 receive one edge, respectively, of the bottom and top spline seals (not shown) that are positioned in the gap between each adjacent pair of shrouds in the shroud assembly. These spline seals again generally conform to or assume the same shape as the respective slot 292 and 294. As also shown in FIGS. 4 and 5, slot 292 also has a plateau shaped or xe2x80x9chumpedxe2x80x9d section 298. In FIGS. 4 and 5, this xe2x80x9chumpedxe2x80x9d section of slot 292 (and the respective spline seal) curves upwardly in the forward section of the shroud before reaching exit holes 288, 289), extends across and above holes 288, 289, and then curves downwardly once past holes 288, 289 in the aft section of the shroud so that cooling air exiting these holes is localized in the region of this humped section 298.
Yet a further prior approach to shroud cooling is shown in FIG. 6 of the present application. The prior shroud of FIG. 6 has a pattern of three rows cooling holes or passages 382, 384 and 386 that are formed in shroud segment 322 and exit through the inner surface of base 344, the forward or leading edge 345, the aft or trailing edge 348, and the side panels or rails 350. A set of three passages, indicated by 388, exit through one of the side panels 350, and are skewed in a direction opposed to the main gas stream. However, the passage 388 closest to the trailing edge is perpendicular to the side panel or only slightly skewed in the direction opposed to the main gas stream. Another set of two passages, indicated by 389, extend through the other side panel 350, both being skewed in a direction opposed to the main gas stream. Because passages 388 and 389 exit through both side panels 350, the prior shroud of FIG. 6 provides impingement cooling to both of the side panels of each adjacent pair of shrouds in the shroud assembly. However, most of the passages 388 and 389 also exit side panels 350 in the forward section of the prior shroud of FIG. 6. As a result, most of the cooling air exiting these holes 388 and 389 tends to be localized in the forward section of the prior shroud of FIG. 6. Also, as shown in FIGS. 7 and 8, the spline seal slot 392 in side panels 350 of the prior shroud of FIG. 6 has an L-shaped section 398 that extends across and above the exit holes 388 and 389, respectively, but curves downwardly about midpoint of panel 350. (Also shown in FIGS. 7 and 8 are top seal slot 394 and aft seal slot 396.) As a result, the spline seal received by slot 392 of each panel also conforms to the shape of section 398 and thus tends to localize the cooling air exiting holes 388 and 389 in the forward section of the prior shroud of FIG. 6, i.e., towards the leading edge 345 of the shroud. In addition, because section 398 of slot 392 is further up side panel 350, more of leading edge 345 of the shroud is exposed to the hot gas from the main gas stream, thus potentially requiring additional cooling air to be used.
Accordingly, it would desirable, therefore, to provide a shroud and resulting shroud assembly for a high pressure turbine that provides cooling air that exits holes or passages in the shroud that minimizes or avoids hot gas ingestion and localizes more of the cooling air exiting from these holes or passages in the region of the side panels from about the midpoint thereof forward to the leading edge and particularly in the region about the midpoint of the side panel. It would also be desirable to provide a shroud and shroud assembly where the cooling air exiting from these holes or passages provides more uniform impingement cooling to each side panel of each adjacent pair of shrouds of the shroud assembly, particularly in the region about the midpoint of each respective side panel.
The present invention relates to a turbine engine cooling component such as a cooling shroud segment for turbine engines such as high pressure turbines that provides improved cooling in the region of the side panels from the midsection thereof forward to the leading edge and particularly in the midsection of the side panel, while minimizing or avoiding hot gas ingestion by the cooling holes or passages exiting such side panels. This turbine engine components comprises:
(a) a circumferential leading edge;
(b) a circumferential trailing edge spaced from the leading edge;
(c) an arcuate base connected to the trailing and leading edges and having a back surface and an arcuate inner surface that is in contact with the main (hot) gas stream of the turbine engine moving in the direction from the leading edge to the trailing edge of the turbine component;
(d) a pair of spaced opposed side panels connected to the leading and trailing edges, each of the side panels having a leading section, a midsection and a trailing section;
(e) a plurality of cooling air passages extending through the base from the back surface thereof and having outlets exiting from at least one of the leading edge, the side panels and the inner surface of the base;
(f) wherein all of the plurality of cooling air passages having outlets that exit from the leading or midsections of each side panel are skewed so that cooling air exits therefrom in a direction opposed to the main hot gas stream;
(g) wherein at least one of the plurality of cooling air passages has an outlet that exits in the midsection of each side panel; and
(h) a spline seal slot that extends from the leading section to the trailing section of the side panel and has a humped section in at least the midsection of the side panel that is above and across at least the outlets of the cooling air passages exiting from the midsection of the side panel.
The present invention further relates to a turbine cooling subassembly comprising a pair of such adjacent turbine components, and having:
(a) opposed adjacent side panels having a gap therebetween and wherein the spacing of the outlets of the cooling air passages exiting from each of the adjacent side panels is staggered such that the outlet of each passage exiting from one of the adjacent panels is not directly opposite outlet of each cooling air passage exiting from the other of the adjacent side panels;
(b) at least one spline seal positioned in the gap between the opposed adjacent side panels and including a pair of spaced edges having a length and thickness such that each of the edges is capable of being received by the slot of one of the adjacent side panels.
The turbine cooling component of the present invention is particularly useful in providing effective, efficient and more uniform cooling, especially to the midsection of the shroud where the temperature of the main hot gas stream tends to be hottest in a high pressure turbine. The skewing of the cooling air passages exiting the side panels in the midsection to forward section of the shroud in a direction opposed to the main gas stream also minimizes or avoids hot gas ingestion by such passages. The turbine cooling subassembly of the present invention that comprises a pair of such turbine components that have staggered or offset outlets for the cooling air passages exiting from the adjacent side panels also provides more uniform impingement cooling coverage. The turbine cooling of the present invention also localizes more of the cooling air exiting these passages in the midsection of the side panels, due to the spline seal slot having the humped section that causes the respective spline seal positioned in the gap between these adjacent shroud segments to also have a humped or hooded configuration.